A. Field of the Invention
This invention relates to a new or improved composite panel structure for use as a decking material in trucks, trailers and other structures, and to such a platform structure incorporating the composite panel.
B. Description of the Prior Art
Over the years, various materials and composites have been used to provide flooring in trucks and trailers, but none has proved to be entirely satisfactory, whether from the point of view of cost, weight, strength, durability, or resistance to corrosion or moisture. Traditional plywood panels cannot meet the stringent performance requirements specific to the truck/trailer industry, particularly as regards strength, durability and resistance to moisture exposure, and other adverse and degrading conditions. Hardwood based products in solid timber form or glued-laminate form are currently used as flooring material in trucks and trailers, but these materials are heavy, not moisture resistant, expensive and of limited availability.
A typical trailer or truck flooring assembly as shown in the prior art employs predominantly 11/8 in. or 13/8 in. thick pieces of random length lumber with a width between 5 in. and 8 in. Other thicknesses (e.g. 11/2 in.) are also used, although less frequently. The edges of individual pieces are machined to provide a profile such as shiplap, or tongue and groove. Individual pieces are thus assembled, side by side, and fastened to the supporting cross-members to constitute the flooring assembly.
Several species of wood are used for this application. The most widely used commercial species group is known as Apitong, and is otherwise referred to as Keruing. More than 70 individual species make up this group, and are widely scattered throughout the Indo-Malayan region, and some South American and African regions. Three principal characteristics inherent to the species of this group include: (1) superior structural strength, (2) superior resistance to wear, and (3) durability (i.e. decay resistance). From these characteristics, Apitong has established itself as the preferred material for use as flat platform trailer flooring. Softwood species of the Southern Yellow Pine group, Douglas Fir (Pseudotsuga menziesii), and Yellow Cedar (Chamaecyparis nootkatensis) are also used, although in limited volumes due to their poor durability characteristics, generally inferior structural properties when compared with hardwood species of the Apitong group, and poor surface resistance to wear. These species are used in somewhat less demanding applications, when weight optimization is a primary objective, and a limited life expectancy can be accepted.
Softwood plywood panels are also being used as flooring material, although to a very limited extent. Factors impeding wider acceptance and use of softwood plywood panels include: (1) their relatively inferior structural capabilities, considering the specific requirements for the particular end-use, (2) their poor wear resistance, and (3) their inherent sensitivity to conditions of moisture exposure.
Several attempts have also been made to develop plywood panels with surface coatings to improve resistance to wear. These attempts, however, have consistently failed to gain any sort of tangible recognition by flat platform trailer manufacturers, most probably owing to the inherent lower structural properties and moisture susceptibility of the panels. For essentially the same reasons, and perhaps because of economic considerations, hardwood plywood panels are generally not used as flooring material for flat platform trailers.
Two factors adversely affect the continued use of the Apitong resource over the long term. Firstly, the high relative density values of approximately 0.57 to 0.65 represent a significant weight disadvantage to an industry deeply concerned with optimization of the weight. More importantly, the continued market availability of tropical hardwoods is increasingly in question, as the source countries develop their domestic industries, other end-uses place new demands on the product, and finally as global environmental concerns regarding the harvesting of the tropical rain forests mount.
Although the softwood species of the Southern Yellow Pine group, Douglas Fir, and Yellow Cedar offer a weight advantage over Apitong, extensive use of lumber and plywood from these species is discouraged by their poor durability, poor surface resistance, and markedly inferior structural properties, as previously described.